Interspinous process spacers

ABSTRACT

Interspinous implants including a spacer configured to fit between first and second adjacent spinous processes of a human spine, to maintain a minimum separation between the spinous processes. An implant also includes a fixation portion coupled to the spacer, in which the fixation portion engages at least one spinous process to hold the spacer in a stable position relative to the spinous process. An implant may be monolithic, non-fillable, and may be inserted between the spinous process from a lateral approach. The fixation portion may be configured as a bracket which can substantially encircle the spinous process, or as flanges which engage lateral sides of the spinous process(es). The spacer may be resilient, and may be expandable along the anterior/posterior direction between the spinous processes. An implant may provide resilient resistance during extension, and/or a uniform extension stop between the spinous processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the following, which areincorporated herein by reference:

U.S. Provisional Patent Application No. 60/910,834, filed Apr. 10, 2007,and is entitled INTERSPINOUS PROCESS SPACER FOR UNILATERAL INSERTION;and

U.S. Provisional Patent Application No. 60/916,098, filed May 4, 2007,and is entitled INTERSPINOUS PROCESS SPACER WITH AT LEAST TWO FLANGESAND ONE TETHER.

BACKGROUND OF THE INVENTION

The invention relates to interspinous devices which may be used toseparate the vertebrae in order to relieve pain and/or other symptomscaused by a collapse of the normal intervertebral spacing. The presentinvention generally describes an interspinous process spacer which maybe placed between two adjacent spinous processes to provide a minimumseparation between the two spinous processes.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 is a perspective view of a portion of a spine;

FIG. 2 is a lateral perspective view of an interspinous spacer implantimplanted between two vertebrae in a portion of a spine;

FIG. 3A is a perspective view of the implant of FIG. 2, in an openconfiguration; and FIG. 3B is a perspective view of the implant of FIG.2 in a closed configuration;

FIG. 4 is a perspective view of an alternative embodiment of aninterspinous spacer implant;

FIG. 5 is a perspective view of an alternative embodiment of aninterspinous spacer implant;

FIG. 6 is a perspective view of an alternative embodiment of aninterspinous spacer implant;

FIG. 7 is a perspective view of an alternative embodiment of aninterspinous spacer implant;

FIG. 8A is a perspective view of an alternative embodiment of aninterspinous spacer implant; and FIG. 8B is a lateral view of theimplant of FIG. 8A;

FIG. 9 is a lateral perspective view of an interspinous spacer implantimplanted between two vertebrae in a portion of a spine;

FIG. 10A is a posterior view of the implant of FIG. 9; and FIG. 10B is alateral view of the implant of FIG. 9;

FIG. 11 is a posterior view of an embodiment of an interspinous spacerimplant with a tether, implanted between two vertebrae in a portion of aspine;

FIG. 12A is a lateral view of the implant of FIG. 11; and FIG. 10B is aposterior view of the implant of FIG. 11;

FIG. 13A is a lateral view of the implant of FIG. 11 in ananterior-posterior orientation in an interspinous gap between twospinous processes; and FIG. 13B is a lateral view of the implant of FIG.11 in a cephalad-caudal orientation;

FIG. 14 is a perspective view of an alternative embodiment of aninterspinous spacer implant in an open configuration;

FIG. 15A is a lateral view of the implant of FIG. 14 implanted betweentwo vertebrae in a portion of a spine and in a closed configuration; and15B is a lateral view of the implant of FIG. 15A in an openconfiguration;

FIG. 16A is a lateral perspective view of an alternative embodiment ofan interspinous spacer implant; and FIG. 16B is a posterior view of theimplant of FIG. 16A;

FIG. 17A is a lateral perspective view of an alternative embodiment ofan interspinous spacer implant; and FIG. 17B is a posterior view of theimplant of FIG. 17A;

FIG. 18A is a lateral perspective view of an alternative embodiment ofan interspinous spacer implant; and FIG. 18B is a posterior view of theimplant of FIG. 18A;

FIG. 19A is a lateral view of an alternative embodiment of aninterspinous spacer implant, implanted between two vertebrae in aportion of a spine; and FIG. 19B is a posterior view of the implant ofFIG. 19A;

FIG. 20A is a lateral view of an alternative embodiment of aninterspinous spacer implant; and FIG. 20B is a posterior view of theimplant of FIG. 20A;

FIG. 21A is a posterior-lateral view of an alternative embodiment of aninterspinous spacer implant with a tether, implanted between twovertebrae in a portion of a spine; and FIG. 21B is a cephalad-lateralview of the implant of FIG. 21A;

FIG. 22A is a posterior-lateral view of an alternative embodiment of aninterspinous spacer implant; FIG. 22B is a posterior-lateral view of aspacer of the implant of FIG. 22A; and FIG. 22C is a cephalad-lateralview of a blocker element of the implant of FIG. 22A;

FIG. 23 is a lateral perspective view of an alternative embodiment of aninterspinous spacer implant with two tethers, implanted between twovertebrae in a portion of a spine;

FIG. 24A is a posterior-lateral view of an alternative embodiment of aninterspinous spacer implant; FIG. 24B is a posterior-lateral view of aspacer and a flange crossbar of the implant of FIG. 24A; and FIG. 24C isa posterior-lateral view of the flange crossbar of FIG. 24B;

FIG. 25 is a posterior perspective view of three alternative embodimentsof an interspinous spacer implant;

FIG. 26 is a posterior-lateral view of three alternative embodiments ofan interspinous spacer implant; and

FIG. 27 is a posterior-lateral view of two alternative embodiments of aninterspinous spacer implant.

DETAILED DESCRIPTION

The present invention relates to orthopedic devices and relatedimplantation instruments and methods. Although the examples providedherein relate to an interspinous spacer, the systems and methodsdescribed herein may be readily adapted for a wide variety of implantsand procedures. Accordingly, the scope of the present invention is notintended to be limited by the examples discussed herein, but only by theappended claims.

Referring to FIG. 1, a perspective view illustrates a portion of a spine10. FIG. 1 illustrates only the bony structures; accordingly, ligaments,cartilage, and other soft tissues are omitted for clarity. The spine 10has a cephalad direction 12, a caudal direction 14, an anteriordirection 16, a posterior direction 18, and a medial/lateral axis 20,all of which are oriented as shown by the arrows bearing the samereference numerals. In this application, “left” and “right” are usedwith reference to a posterior view, i.e., a view from behind the spine10. “Medial” refers to a position or orientation toward a sagittal plane(i.e., plane of symmetry that separates left and right sides from eachother) of the spine 10, and “lateral” refers to a position ororientation relatively further from the sagittal plane. In thisapplication, “superior” refers to a position or orientation in thecephalad direction 12, and “inferior” refers to a position ororientation in the caudal direction 14.

As shown, the portion of the spine 10 illustrated in FIG. 1 includes afirst vertebra 24, which may be the L5 (Fifth Lumbar) vertebra of apatient, and a second vertebra 26, which may be the L4 (Fourth Lumbar)vertebra of the patient. The systems and methods may be applicable toany vertebra or vertebrae of the spine 10 and/or the sacrum (not shown).In this application, the term “vertebra” may be broadly interpreted toinclude the sacrum.

As shown, the first vertebra 24 has a body 28 with a generally disc-likeshape and two pedicles 30 that extend posteriorly from the body 28. Aposterior arch, or lamina 32, extends between the posterior ends of thepedicles 30 to couple the pedicles 30 together. The first vertebra 24also has a pair of transverse processes 34 that extend laterally fromthe pedicles 30 generally along the medial/lateral axis 20, and aspinous process 36 that extends from the lamina 32 along the posteriordirection 18.

Similarly, the second vertebra 26 has a body 48 from which two pedicles50 extend posteriorly. A posterior arch, or lamina 52, extends betweenthe posterior ends of the pedicles 50 to couple the pedicles 50together. The second vertebra 26 also has a pair of transverse processes54, each of which extends from the corresponding pedicle 50 generallyalong the medial/lateral axis 20, and a spinous process 56 that extendsfrom the lamina 52 along the posterior direction 18. The vertebrae 24,26 are separated from each other by an intervertebral disc 60.

Referring to FIG. 2, a perspective view illustrates one embodiment of animplant 100, which may be termed an interspinous spacer, implantedbetween two adjacent vertebrae 24, 26. Implant 100 comprises a fixationportion which is a bracket 110, joined to a spacer 120. The bracket 110may comprise a collar 112 which is shaped to substantially encircle andgrip the spinous process 36. The collar has a first end 114 (shown inFIG. 3A) and a second end 116, and rims may be formed at the opposingends of the collar 112 to assist the collar in securely gripping thespinous process.

A portion of the collar 112 comprises a spring member 118. As seen inFIG. 3A, when the spring member 118 is in one shape, the bracket 110 isat a first stable low energy configuration, in which the collar is“open” and the ends 114, 116 are spaced relatively far apart. As seen inFIG. 3B, when the spring member 118 is in a second shape, the bracket110 is at a second stable low energy configuration, in which the collaris “closed” and the ends 114, 116 are spaced relatively closer together.The bracket 110 is reversibly transformable, meaning it is transformablefrom the first configuration to the second configuration and from thesecond configuration to the first configuration. Transformation may beattained by positioning the bracket: for example, pushing the “open”bracket against the side of the spinous process may move the springmember 118 from the first shape to the second shape, transforming thebracket from the first open configuration to the second closedconfiguration. Transformation may also be attained by pushing thebracket toward the second configuration. This transformation may besimilar to that found in a common hair barrette which snaps from a firstopen configuration to a second closed configuration when pressed againsta surface. When the bracket 110 is closed around the spinous process inthe second low energy configuration, such as in FIG. 2, the bracketsubstantially encircles the spinous process and the spacer 120 isretained by the spinous process and held in a stable position relativeto the spinous process. A stable position is one in which a micro amountof relative motion may be possible, but not gross migration of thespacer. Transformation of the bracket from the open configuration to theclosed, and vice versa, may be referred to as toggling, where togglingis defined as moving between the two different stable low-energyconfigurations. Toggling of the bracket between configurations may takeplace in situ, after the spacer has been placed between the spinousprocesses.

Bracket 110 may be described as bi-stable, meaning that it can attaintwo different stable low-energy configurations. A low-energyconfiguration is a configuration in which a relative local minimum ofenergy is stored. Energy types may includes kinetic, thermal, resilientor any other type of energy. Bracket 110 stores resilient energy, whichmay be also called stored spring force.

Implants with a bracket 110 fixation portion may be insertedunilaterally. From either lateral approach, an opening is created toaccess the spinous process gap at the targeted vertebral level, betweenan inferior spinous process of one vertebra and the superior spinousprocess of the adjacent second vertebra. The spacer and superior end ofthe bracket are inserted into the gap, and the spacer is moved to adesired orientation relative to the spine. The desired orientation maybe between the inferior and superior spinous processes. The bracket isrotated toward the inferior spinous process, and positioned against theinferior spinous process. The bracket is urged against the inferiorspinous process until the bracket snaps closed around the inferiorspinous process. When the bracket is thus coupled to the inferiorspinous process, the spacer is oriented toward the superior spinousprocess, and superior to the bracket, as seen in FIG. 2.

The spacer of the implant may be formed and shaped in a variety of ways.In the embodiment depicted in FIGS. 2 and 3, the spacer 120 has aregular arcuate shape and is hollow and open posteriorly. An outer wall122 forms the superior side of the spacer, and an inner wall 124 formsthe inferior side of the spacer. As seen in FIG. 3B, a radial dimension126, measured normal to the curve of the outer wall 122, issubstantially constant between the outer wall 122 and the inferiorspinous process 36. The radial dimension 126 may also be called a spaceroffset dimension. During extension, the superior spinous process 56 maycontact the outer wall 122 and urge the outer wall 122 toward the innerwall 124. As the distance between the walls 122, 124 grows shorter,progressive resistance may occur, in which increasing force is requiredto move an additional distance. When the outer wall 122 contacts theinner wall 124 and the inner wall 124 contacts the inferior spinousprocess 36, an extension stop occurs, wherein extension is physicallylimited by the contact between the walls and the process, and canproceed no further. The spacer 120 may also be configured to becompliant, or resilient, providing variable resistive force which urgesthe superior and inferior spinous processes apart in response toextension of the spine.

The regular arcuate shape of the spacer provides a constant spaceroffset dimension between the spinous processes 36, 56 regardless oftheir relative orientation through a range of motion. In addition, auniform extension stop may be provided, in which the stop occurs at thesame distance between the spinous processes regardless of the relativeorientation of the spinous process. Therefore, even as a patient bendslaterally during extension, thus changing the relative orientation ofthe spinous processes, a constant spacer offset dimension is providedand a uniform extension stop at that vertebral level. The spacermaintains a minimum distance between the adjacent spinous processes atthat level.

A uniform extension stop is a stop or spacer which providessubstantially the same separation between adjacent spinous processes,regardless of the relative orientation of the spinous processes due, forexample, to the patient's posture at any given moment. For example, thepatient's spine could be in extension combined with axial or lateralrotation. The 3D profile or surface of a uniform extension stop could becreated, for example, by offsetting the 3D surface of one of the spinousprocesses by a constant dimension so that each point on the originalsurface translates along a vector normal to the surface at that point.This method could also be used with an approximate surface composed ofnumerous small triangular facets, where each facet is offset by aconstant dimension along its normal vector, and all the resulting facetsare trimmed with respect to each other. The approximation could becarried further by creating a small set of original surfaces thatencompasses the morphological variances seen in a larger set of anatomicdata from, for instance, CT scans of real patients. The set of originalsurfaces would then be uniformly offset as described above. Contemporary3D CAD software is adept at this sort of transformation. Approximationof many individual surfaces down to a small set of sizes remains in thespirit of uniformity, since it is common practice to generate a sizerange in many products, from hip stems to jeans. The end result would bea family of spacers which vary by internal configuration (several sizesto provide a close fit to the spinous process) and by spacer dimension(several sizes to provide the necessary amount of separation betweenspinous processes).

FIGS. 4-7 illustrate additional embodiments of interspinous spacerimplants comprising the bracket 110 and a spacer. The embodimentsdescribed may be implanted as illustrated in FIG. 2, in which the spaceris positioned on the superior side of the bracket 110. However, it isappreciated that, alternatively, the spacers may be shaped andconfigured to be positioned on the inferior side of the bracket 110, andtherefore be positioned on the inferior side of a superior spinousprocess 56 adjacent to an inferior spinous process 36.

Referring to FIG. 4, an alternative embodiment of an implant comprisingthe bracket and an alternative spacer is shown. Implant 150 includes thebracket 110, which is coupled to a spacer 152. Spacer 152 also has aregular, arcuate shape, and is formed of a series of resilientplate-like flanges 154 interleaved with gaps 156. When the bracket 110is coupled to an inferior spinous process as in the method set forthpreviously, the flanges 154 extend substantially perpendicular to thespinous process. During extension, as the superior spinous processcontacts and deforms the spacer 152, the flanges 154 sequentiallydeflect, providing compliant resistance, which may nonlinearly increaseas extension continues. This configuration may provide a uniformextension stop with a constant spacer offset dimension.

Referring to FIG. 5, another alternative embodiment of an implantcomprising the bracket and an alternative spacer is shown. Implant 160includes the bracket 110, which is joined to a spacer 162. Spacer 162has a regular, arcuate shape, and is formed of a series of flanges 164interleaved with gaps 166. The flanges 164 are not plate-like but have acentral cut-out 168 so that the spacer 162 is hollow and open bothanteriorly and posteriorly. During extension, as the superior spinousprocess contacts and deforms the spacer 162, the flanges 164sequentially deflect, providing soft resistance, which may nonlinearlyincrease as extension continues. This configuration may provide auniform extension stop with a constant spacer offset dimension. Implants150 and 160 may include flange designs that are optimized to providedesired flexibility and a definite endpoint or extension stop.

Referring to FIG. 6, yet another alternative embodiment of an implantcomprising the bracket and an alternative spacer is shown. Implant 170includes the bracket 110, which is joined to a spacer 172. Spacer 172 issimilar in configuration to spacer 120, except that spacer 172 is openboth anteriorly and posteriorly, forming a closed loop shape. Thisconfiguration may provide levels of flexibility and resilience thatdiffer from other embodiments.

Implants 100, 150, 160, and 170 are each shaped so that each may providea constant spacer offset dimension, and a uniform extension stop. Thespacer offset dimension may vary, and may be tailored to replicatenormal human physiological biomechanics. Additionally, a medial-lateralwidth of the spacer may be variable to accommodate the expected range ofmotion of adjacent spinous processes.

Referring to FIG. 7, yet another alternative embodiment of an implantcomprising the bracket and an alternative spacer is shown. Implant 180includes the bracket 110, which is joined to a spacer 182. Spacer 182comprises concentrically arranged semi-cylindrical flanges, includingouter flange 184 and inner flange 186. Although two flanges are includedin this embodiment, alternative implants may comprise onesemi-cylindrical flange, or several, arranged concentrically. Theflanges 184, 186 are positioned such than an exterior wall 188 of thesemi-cylinder formed by the flanges extends antero-posteriorly when theimplant is secured to a vertebra. An anterior-posterior height of thespacer 182 may exceed a medial-lateral width of the spacer member.During extension, the superior spinous process may contact the outerflange 184, which deflects and may eventually contact inner flange 186,providing a nonlinear increase in resilient force. Implant 180 mayprovide flexibility, and a uniform extension stop.

Referring to FIGS. 8A and 8B, another alternative embodiment of animplant comprising the bracket and an alternative spacer is shown.Implant 190 includes the bracket 110, which is joined to a spacer 192.Similar to implant 180, spacer 192 comprises concentrically arrangedsemi-cylindrical flanges, including outer flange 194 and inner flange196. However, in this embodiment the flanges 194, 196 are positionedsuch than an exterior wall 198 of the semi-cylinder formed by theflanges extends medial-laterally when the implant is secured to avertebra. A medial-lateral width of the spacer 192 may exceed ananterior-posterior height of the spacer member. During extension, thesuperior spinous process may contact the outer flange 194, whichdeflects and may eventually contact inner flange 196, providing anonlinear increase in resilient force. Implant 190 may provideflexibility, and a uniform extension stop.

Referring to FIG. 9, a perspective view illustrates one embodiment of animplant 200, which may be termed an interspinous spacer, implantedbetween two adjacent vertebrae 24, 26. Implant 200 comprises a spacer202 and a fixation portion comprising two flanges 204, 206. Whenimplanted between two vertebrae 24, 26 and positioned to a desiredorientation, the two flanges 204, 206 may engage opposite lateral sidesof the inferior spinous process 36, to secure and retain the spacerrelative to the spinous process. The implant remains in its implantedlocation through the full range of spinal motion.

FIG. 10A is an anterior view of implant 200, and FIG. 10B is a lateralview of one lateral side of the implant. Referring to FIG. 10A, spacer202 has a first end 208 from which flange 204 extends orthogonally, anda second end 210 from which flange 206 extends orthogonally. Flange 204has an inner wall 212, and flange 206 has an inner wall 214, and the twoinner walls 212, 214 are angled so that the flanges taper and theimplant forms an approximate “V” shape. The inner walls 212, 214converge at a saddle 216. The angles of the inner walls 212, 214, andthe shape of the saddle 216 may vary, so that variations in size andprofile of different spinous processes may be accommodated. Similarly,the lengths of the flanges, and width of the spacer may vary. The spacermay comprise a compliant, resilient material, or a rigid material, ormay comprise a layered configuration with compliant materials layeredover rigid elements.

As seen in FIG. 10B, a lateral profile of the implant resembles a smoothexaggerated egg shape, with the flanges tapering in height from acephalad end 218 to a caudal end 220. Implant 200 may be monolithic, andmay be bilaterally symmetrical, in this instance meaning it issymmetrical on either side of the sagittal plane. An insertion feature222 is near the cephalad end 218. In this embodiment of the inventionthe insertion feature 222 is hexagonally shaped, to accommodate ahexagonal driver. However, the insertion feature could have any shape inplace of hexagonal, such as square, hexalobular, oval, or paired holes.In addition, the insertion feature could be internal as shown, orexternal, or could extend along the outer surface of the flange ifnecessary. The insertion feature may be located only on one side of animplant, or on both sides.

The insertion feature 222 opens into a hollow 224 which extends thelength of the spacer 202. This hollow spacer allows for intrinsic springaction when, during extension, the superior spinous process pushesagainst the spacer member 202. Non-linearly increasing resistance, and adefinite extension limit with a minimum separation, may be provided byimplant 200. Implant 200 may also provide a variable extension stop

Referring to FIG. 11, an anterior view alternative embodiment of aninterspinous implant with an optional tether is illustrated, implantedbetween two vertebrae 24, 26. Implant 250 is generally “V” shaped andcomprises a spacer 252 and a fixation portion comprising two flanges254, 256. Flanges 254, 256 are shaped to engage the opposite lateralsides of the spinous process 36, to retain the spacer relative to thespinous process. A tether 258 is connected to flange 256, extends aroundspinous process 36, and is connected on the far lateral side to flange254. Together, the tether, flanges and spacer fully encircle theinferior spinous process 36. Similar to implant 200, implant 250 may bebilaterally symmetrical.

Referring to FIGS. 12A and 12B, lateral and posterior views of implant250 and tether 258 are shown. From the lateral perspective, implant 250has an elongated egg shape. The spacer 252 has a substantially arcuateshape with a rounded superior wall 260 and an insertion feature 262which opens into a hollow 264. In this embodiment, a first end 266 and asecond end 268 of the spacer 252 have flat lateral surfaces, but inother embodiments those surfaces may be rounded. The flanges 254, 256extend orthogonally from the spacer 252, and taper both in height andwidth. The flanges 254, 256 converge at a saddle 270, which may becontoured to accommodate the superior profile of an inferior spinousprocess. The saddle and flanges may be sized and shaped for a preferredfit between the flanges and the spinous process to limit lateralmovement of the spacer and to retain the implant relative to theinferior spinous process. The flanges may be of any length. The lateralprofile shape of the implant could be as depicted, or could be oval,paisley-shaped, or kidney-shaped, among others. The hollow configurationof the spacer may provide intrinsic resilient spring action duringextension, and the rounded superior wall of the spacer may provide aminimum separation distance between the spinous processes and a uniformextension stop. The configuration of the spacer may also providevariable resistive force urging the inferior and superior spinousprocesses apart in response to extension of the spine.

At tapered end of flange 254 is located a tether attachment feature 272,and at the end of flange 256 is tether attachment feature 274.Attachment features 272, 274 each comprise an opening through which atether may pass. Once passed through an attachment feature 272, 274, thetether may be secured, either to the implant 250, or to itself to form acontinuous loop. Methods of securing the tether may include tying asurgical knot or knots, crimping a fastener to the tether, or using asecuring device such as a knotless line lock, among others. Thecombination of flanges and tether(s) secures the spacer to one of thespinous processes, snugly or loosely as appropriate. Thus the spacerstays in its installed location in extension, due to the pinching actionof the spinous processes against the central spacer portion and theaction of the flanges against the sides of the spinous process. It alsostays in place in flexion due to the action of the tether around one ofthe spinous processes.

FIGS. 13A and 13B illustrate one method for the insertion andpositioning of implant 250. It is appreciated that other implantsdescribed herein with similar shapes, such as implants 200, 280 and420-470 may be inserted and positioned in a similar manner. Implant 250may be inserted unilaterally from the right or left side of the spinousprocesses, and does not require disruption of the supraspinous ligament.The implant is inserted medially into the interspinous process gap in ananterior-posterior orientation, with the spacer 252 anteriormost and thetips of the flanges 254, 256 posteriormost, as seen in FIG. 13A. Oncethe spacer 252 has reached a desired medial-lateral location in theinterspinous process gap with the saddle lined up with the spinousprocesses, the spacer 252 is rotated in the direction of the arrow 276until the flanges reach a desired position on either side of theinferior spinous process 36, seen in FIG. 13B. The torque to rotate thespacer 252 may be provided by an instrument (not shown) configured tomate with insertion feature 262, or may be provided by simply pushingthe accessible flange in the direction of arrow 276. Since both flangesare orthogonal to the spacer member and parallel to one another, theywill move simultaneously on opposite sides of the spinous process as thespacer is rotated. It is appreciated that, if desired, the spacer couldbe rotated in an anterior-cephalad direction until the flanges reachpositions on either side of the superior spinous process 56.

Other methods of implantation and positioning may be used. For example,if the lateral length of the implant, from the superior wall 260 to thetips of the flanges, exceeded the anterior-posterior dimension of theinterspinous gap, an alternative implantation method could beimplemented. The implant could be inserted obliquely until its flangeends bracket the supraspinous ligament, then rotated about thesupraspinous ligament in the transverse plane until the spacer restsbetween the spinous processes. Then the implant could be rotated aboutthe spacer in the sagittal plane until the flanges rest beside one ofthe spinous processes.

The tether 258 may comprise commercial suture, such as #2 or #5 braidedpolyester suture, a broad, flat braided tape, surgical cable or wire, orany flexible strand. The tether may be connected to one or both flangesprior to implantation, or connected to one flange and passed through theopposite tether attachment feature, or not connected to the implant atall prior to implantation. Connection to the flanges may be throughknotting, crimping, gluing, over-molding, insert molding, or the tethermay be formed from implant substrate material. The tether may be securedto itself, to one or both attachment features, or to a separateattachment component such as a suture clip. A second tether may beincluded and secured around the superior spinous process, if desired.Use of one tether may assist in retaining the implant. Addition of asecond tether may provide motion restriction when the patient moves intoforward flexion.

The tether may be positioned around the spinous process by means of acannulated instrument resembling a shepherd's crook. The tether may bepre-loaded in the crook, or passed through the crook after the crook ispositioned. The crook may be positioned around the spinous process andthe tether delivered through the crook. A first end of the tether may beconnected to one flange of the implant, and the implant inserted orpushed into the interspinous gap while simultaneously, the tether ispulled back through the crook, helping to pull the implant into theinterspinous gap. After the implant is in its desired position in theinterspinous gap, and rotated so that the flanges are on either side ofthe spinous process such as in FIG. 13B, the free or second end of thetether may be connected to the other, accessible flange. Alternately, ashaped suture grasper could be used to place the tether.

Referring to FIG. 14, a perspective view shows an implant 280. Implant280 comprises a spacer 282, and two flanges 284, 286 which are coupledto the spacer in a substantially orthogonal orientation, similar to theV-shaped configuration of implants 200 and 250. A portion of spacer 282may be expanded in the anterior-posterior orientation to restrictrotation of the spacer out of a desired orientation relative to thespine. The expanded spacer may also provide resilient resistance betweenthe spinous processes during extension.

Spacer 282 comprises a first spacer member 288 and a second spacermember 290. Spacer member 288 may be substantially hollow, and has aninsertion feature 287. Spacer member 290 is shaped to mate with spacermember 288, and has an insertion feature 291. Spacer members 288 and 290may be configured to fit together such that when held together they aresized to fit into the interspinous gap. After insertion, the implant 280may be rotated until the flanges 284, 286 reach a desired position oneither side of the spinous process 36, as seen in FIG. 15A. Once sopositioned, the spacer members 288 and 290 may be released and allowedto expand in the anterior-posterior plane, as seen in FIG. 15B. Duringexpansion, one or both of the spacer members 288, 290 may move.

Returning to FIG. 14, each flange 284, 286 is substantially V-shaped.Flange 284 comprises a posterior strut 292 and an anterior strut 294which are joined at an elbow 285. Similarly, flange 286 comprises aposterior strut 296 and an anterior strut 298 joined at an elbow 287.The flanges 284, 286 each have intrinsic spring action, such that ifposterior strut 292 and anterior strut 294 (or posterior strut 296 andanterior strut 298) are held together then released, the flange willspring back to the low energy point V shape. Spacer member 288 iscoupled to and extends between the posterior struts 292, 296. Spacermember 290 is coupled to and extends between the anterior struts 294,298. Consequently, spacer members 288, 290 may be held together in aclosed position. When released, they will intrinsically move into anopen position.

Spacer 280 may be unilaterally inserted between the spinous processesand rotated in a manner similar to that described for implant 250 anddepicted in FIGS. 13A and 13B. An insertion tool or tools (not shown)may engage in insertion features 287, 291, and pinch the spacer members288, 290 together. The implant 280 is fit into the interspinous gap withthe spacer 282 oriented anteriormost and the elbows 285, 287 of theflanges posteriormost. Once the implant 280 reaches a desiredmedial-lateral orientation, it may be rotated until the flanges 284, 286are in a desired position on either side of spinous process 36. At thispoint, the tool may be disengaged, or the spacer members otherwisereleased, from the spacer, allowing the spacer to expand in theanterior-posterior plane to attain the open position. The spacer mayprovide compliant, resilient resistance as the distance between thespinous processes decreases during extension, and a uniform extensionstop at a minimum separation distance. Optionally, a tether maycooperate with the flanges or the hollow spacer member to retain theimplant relative to a spinous process.

FIGS. 16-18 illustrate alternative embodiments of implants with spacerswhich may expand in the anterior and/or posterior direction afterimplantation. FIG. 16A is a lateral perspective view of an implant 300which comprises a spacer 302, paired inferior flexible flanges 304 andpaired superior flexible flanges 306. FIG. 16B is a posterior view ofimplant 300. The spacer 302 comprises a first spacer portion 308 and asecond spacer portion 309, which are connected by the flexible flanges304, 306. The spacer 302 is configured so that it may be pinched orsqueezed down to a size which may be inserted from a lateral approachinto the interspinous gap. Once inserted, the implant 300 may be rotatedinto a preferred orientation so that the paired inferior flexibleflanges 304 engage and retain the lateral sides of the inferior spinousprocess, and the paired superior flexible flanges 306 engage and retainthe lateral sides of the superior spinous process. The spacer may thenbe released and the first and second spacer portions 308, 309 allowed toexpand along the anterior/posterior direction between the spinousprocesses. The configuration of the spacer portion 302 may provide auniform extension stop at a minimum separation distance.

Referring to FIGS. 17A and 17B, lateral and posterior views of implant310 are shown. Implant 310 comprises a spacer 312, paired inferiorflexible flanges 314 and paired flexible superior flanges 316. Spacer312 further comprises a central portion 313, a superior portion 318connected to the central portion by the flexible superior flanges 316,and an inferior portion 319 connected to the central portion by theflexible inferior flanges 314.

Referring to FIGS. 18A and 18B, lateral and posterior views of implant320 are shown. Similar in configuration to implant 310, implant 320comprises a spacer 322, paired inferior flanges 324 and paired superiorflanges 326. Spacer 322 further comprises a central portion 323, asuperior portion 328 connected to the central portion by the flexiblesuperior flanges 326, and an inferior portion 329 connected to thecentral portion by the flexible inferior flanges 324. The pairedsuperior flanges 326 extend caudally past the spacer 322, such that whenimplanted and rotated, the extended ends of the paired superior flanges326 may be adjacent the lateral sides of the inferior spinous process.

Implants 310 and 320 may be implanted in a similar manner to oneanother. The superior and inferior portions of the spacer may be pinchedor squeezed toward the central portion of the spacer, creating a shapesized to fit into the interspinous gap, with the superior flexibleflanges oriented anteriormost and the inferior flexible flanges orientedposteriormost. The implant is placed in the interspinous gap and rotatedinto a preferred orientation so that the paired inferior flexibleflanges engage and retain the lateral sides of the inferior spinousprocess, and the paired superior flexible flanges engage and retain thelateral sides of the superior spinous process. The spacer may then bereleased and the superior and inferior portions of the spacers allowedto expand anterior-posteriorly between the spinous processes. Implants300, 310 and 320 may provide a uniform extension stop at a minimumseparation distance, and may also provide progressively increasingresilient force as the spinous processes converge during extension ofthe spine. Optionally, a tether such as that set forth previously maycooperate with the flanges to retain implant relative to a spinousprocess.

Referring to FIGS. 19A and 19B, lateral and posterior views of analternate interspinous spacer implant 330 is shown. Implant 330comprises a spacer 332 which may be elongated in an anterior-posteriordimension, lateral flanges 334 and 336, and adjustment member 338, whichmay be a threaded bolt. Implant 330 is configured so that the lateralflanges 334, 336 may be rotated into and out of alignment with thespacer 332. Spacer 332 may comprise more than one component part, andmay include teeth 333 which mesh when the adjustment member 338 isactuated. When the flanges are aligned in profile with the spacer, theimplant has a size and shape which allows it to be inserted into theinterspinous gap from a unilateral approach. Once in the interspinousgap, the flanges 334, 335 may be rotated relative to the spacer 332 sothe flange ends are lateral to and engage the superior and inferiorspinous processes 36, 56, as seen in FIG. 19A. The adjustment member 338may be actuated or tightened to lock down the alignment of the flanges334, 336 relative to the spacer 332. The adjustment member 338 may alsohave an insertion feature 339, which may function as an attachment pointfor tools used in inserting and adjusting the implant. Implant 330 mayprovide a uniform extension stop at a minimum separation distance.

Referring to FIGS. 20A and 20B, lateral and posterior views of analternate interspinous spacer implant 340 is shown. Implant 340 issimilar in configuration to implant 330, with the difference that aspacer 342 is elongated only in a posterior orientation. Implant 340comprises the spacer 342, lateral flanges 344, 346 and an adjustmentmember 338. Spacer 342 may include teeth 343, which may mesh with teethon either or both flanges 344, 346. The adjustment member 338, which maybe a threaded bolt, may include an insertion feature 339 which may matewith insertion and/or adjustment tools (not shown). Implant 340 may beinserted and the flanges 344, 346 rotated in the same manner aspreviously set forth for implant 330. Implant 340 may provide a uniformextension stop at a minimum separation distance.

FIGS. 21A and 21B illustrate an implant system 350 which may optionallybe enhanced in the anterior-posterior dimension. Referring to FIG. 21A,implant 352 is generally H-shaped, with a centrally located spacer 354,a pair of inferior flanges 356 and a pair of superior flanges 358. Thespacer 354 has a plurality of cutouts 359 which may be linear inorientation, to add flexibility to the spacer. A tether 360 loops aroundspinous process 36 and is attached to the inferior flanges 356.Optionally, but not shown, a second tether may be attached to thesuperior flanges 358 and loop around the superior spinous process 56.Referring to FIG. 21B, an optional blocker element 362 may be slidlaterally onto the implant 352 after the implant is implanted betweenthe spinous processes. The blocker element has three sides: a posteriorside 364, a lateral side 366 and an anterior side 368, and is sized andshaped to overlap the implant 352 in the area of the spacer 354. Theblocker element may increase the anterior-posterior dimension of thesystem 350. Additionally, the blocker element may modify the intrinsiccompliance of the system. Whereas the flexible spacer 354 may provide acompliant extension stop between the spinous processes, the blockerelement 362 may provide a rigid extension stop. The anterior 368 and/orposterior 364 sides of the blocker element 362 may be narrower than thespacer 354, in which case both compliant and rigid stops may be providedby the system 350.

Referring to FIG. 22A, a posterior perspective view of an alternateembodiment of a spinous process spacer is shown. Implant 360 includes aspacing element 362 which includes a fixation portion, a blocker element364, and an assembly pin 366. As seen in FIG. 22B, the spacing element362 comprises a spacer 372 coupled to inferior flanges 368 and superiorflanges 370. Grooves 374 are incised into the spacer 372 on the inferiorand superior sides. As seen in FIG. 22C, the blocker element 364comprises a posterior block 376 and a lateral face 378. The assembly pin366, which may be threaded, may pass through a hole in the lateral face378, then into a bore 380 in the spacer 372 to fasten the blockerelement 364 to the spacing element 362, as seen in FIG. 22A.Additionally, one or more tabs 382 on the block 376 may slide into thegrooves 374 on the spacer 372, further securing the blocker element 362to the spacing element 362.

Implant 360 may be assembled in situ in the interspinous gap. Spacingelement 362 may be inserted between the spinous processes and rotateduntil the inferior flanges 368 flank the inferior spinous process, andthe superior flanges 370 flank the superior spinous process. Next theassembly pin 366 may be passed through the hole in the lateral face 378of the blocker element 364. Together the blocker element 364 andassembly pin 366 are assembled, from a lateral approach, onto thespacing element 362 in situ, with the assembly pin 366 fitting into thebore 380, and tabs 382 sliding into the grooves 374. Once at a desiredposition, the blocker element 364 may be locked in place by tighteningthe assembly pin 366. The blocker element 364 may be comprised of apliable material that provides a soft extension stop, while the spacer372 provides a hard extension stop at a minimum separation distance. Theblocker element 364 increases the anterior-posterior dimension of theimplant.

Referring to FIG. 23, an interspinous spacer implant with optionaltethers is illustrated, implanted between two vertebrae 24, 26. Implant390 comprises spacer 392, paired inferior flanges 394, and pairedsuperior flanges 396. An inferior tether 398 is secured around theinferior spinous process 36, and a superior tether 399 is secured aroundthe superior spinous process 56. The combination of flanges andtether(s) secures the spacer to one of the spinous processes, snugly orloosely as appropriate. Thus the spacer stays in its installed locationin extension, due to the pinching action of the spinous processesagainst the central spacer portion and the action of the flanges againstthe sides of the spinous process. It also stays in place in flexion dueto the action of the tether around one of the spinous processes.

The spacer 392 comprises a cavity 400 which extends the full lateralwidth of the spacer. The cavity 400 may have a specific shape, such as ahexagon, enabling it to also serve as an insertion feature which canconnect with tools or instruments which provide torque to rotate thespacer. A plurality of slots 402 extend partially across the spacer 392,giving the spacer additional flexibility during extension and flexion.The implant 390 may be available in a variety of sizes, and in a varietyof anterior-posterior dimensions.

FIG. 24A illustrates another alternative embodiment of an interspinousspacer. Implant 410 comprises a cylindrical spacer 412, a fixationportion which comprises two flange crossbars 414, 416, and may includeone or more fasteners 418. As seen in FIG. 24C, each crossbar 414, 416has a general Z shape such that one end of the crossbar may bepositioned to a location adjacent an inferior spinous process, while theopposite end may simultaneously be located adjacent the opposite lateralside of a superior spinous process. Implant 410 may be assembled insitu. Spacer 412 may be placed into the interspinous gap from a lateralapproach. One flange crossbar such as crossbar 416 is inserted throughthe spacer, as seen in FIG. 24B. The second flange crossbar 214 is theninserted through the spacer; however the crossbars 214, 216 may beinserted in either order. Once both crossbars 414, 416 are in place sothat their ends flank and engage the superior and inferior spinousprocesses, fasteners 418 may be inserted through openings in thecrossbars and the spacer to couple the crossbars to the spacer and lockthe positions of the crossbars. Alternately, the crossbars may haveintegral elements which allow for a snap fit to the spacer 412. Implant410 may allow a variable extension stop in which the spacer 412, or aportion thereof, is compliant and provides a soft extension stop, whilethe crossbars that pass through the center of the spacer provide a hardextension stop.

Referring to FIG. 25, three alternative interspinous spacer implants areshown. Implant 420 comprises a spacer 422, a pair of elongated inferiorflanges 424, and a pair of truncated, rounded superior extensions 426.Implant 420 may comprise a flexible material, and is shaped to beimplanted between the spinous processes from a lateral approach. Atether such as those described previously may be optionally secured tothe inferior flanges 424 and looped around the inferior spinous process.

Implant 430 comprises a spacer 432 and fixation portion which is a pairof inferior flanges 434. The spacer 432 has a rounded superior wall 436,creating an arcuate shape which provides a uniform extension stopregardless of the relative orientation of the spinous processes througha range of motion. A slot 438 is cut in a curved pattern through thespacer 432, providing additional flexibility to the spacer. Implant 440is similar in configuration to implant 430, except that a slot 442 islonger and arranged in more curves through the spacer, and may extendinto one or both flanges. Both implants may provide a nonlinear increasein resilient force during extension, as the portions of the spacer cutby the slot sequentially deflect as the spacer is deformed bycompression between the spinous processes. A tether may be coupled toeither implant to retain the implant to a spinous process.

FIG. 26 illustrates three additional alternative interspinous spacerimplants. Implant 450 comprises a spacer 452 and a pair of flanges 454.The spacer 452 has a plurality of cutouts 456 which are openings throughthe spacer that do not open out to the lateral sides. Implant 420 mayprovide a nonlinear increase in resilient force during extension, as theportions of the spacer cut by the cutouts sequentially deflect as thespacer is deformed by compression between the spinous processes.

Implant 460 comprises a spacer 462 and a pair of flanges 464. Severalcutouts 466 are incised through the spacer 462, and a plurality of slots468 extend medially from the lateral sides of the spacer and theflanges. Implant 470 is similar in configuration to implant 470, exceptthat slots 472 are longer, extending medially farther toward the centerof the implant, and are located farther along the length of the flanges.It is appreciated that a variety of alternative implants could includecutouts and slots of various lengths, widths, depths and locations. Thecutouts and slots may be sized and placed to create preferred levels ofcompliance and resilient force in the implants.

Implants 420, 430, 440, 450, 460, and 470 are sized and shaped to beimplanted using a lateral approach from either side of the spinalcolumn, and without disturbing the supraspinous ligament. Each implantmay be held in an anterior-posterior orientation, with the flangesposteriormost, and inserted into the interspinous gap in thatorientation. After the implant is at a desired lateral position, thespacer may be rotated so that the inferior flanges flank and engage thelateral sides of the inferior spinous process. The spacer stays in itsinstalled location in extension, due to the pinching action of thespinous processes against the central spacer portion and the action ofthe flanges against the sides of the spinous process. Optionally, atether may be coupled to any of the implants to retain the implant tothe inferior spinous process.

Referring to FIG. 27, two alternative embodiments of an interspinousspacer are shown. Implant 480 is generally X-shaped, and has flangeswhich are adjustable by way of a scissor-type hinge. A central pin 482is generally cylindrical, may be threaded and has an adjustable end cap483. The implant 480 also comprises a first diagonal flange 484 and asecond diagonal flange component 486. The flange components 484, 486 aregenerally Z-shaped, and may be identical and differ only in theirorientation in the assembled implant. Each flange component 484, 486 hasa bore through which the central pin 482 fits. The spacing between theflange components 484, 486 may be adjusted by rotating the components484, 486 about the central pin 482; then the end cap 483 may be fastenedto lock down the implant at a preferred flange spacing. Alternately, thecentral pin and end cap may comprise a spring or ratchet which providespressure to the flanges, allowing the flanges to grip the spinousprocesses.

Similar to implant 480, implant 490 has a central pin 492 and may havean end cap 493. The implant also comprises an inner diagonal flangecomponent 494 and an outer diagonal flange component 496. The flangecomponents 494, 496 hinge around the central pin 492. The orientation ofthe flange components 494, 496 may be adjusted by rotating around thecentral pin 492. Like implant 480, the central pin may comprise aspring, ratchet or other member to provide pressure to the flanges.

Implants 480, 490 may be implanted using similar methods. An approach toeither lateral side of the spine may be used. The implant 480 or 490 is“flattened” by loosening the end cap and compressing the flangecomponents toward one another until the implant has a flat profile, withlittle space between the flanges, and the end cap may be tightened tohold this profile. The implant is inserted into the interspinous gap.The flanges are released and allowed to close around the spinousprocesses.

The implants, or components thereof, disclosed herein may be monolithic,or unitary, formed as one piece. The implants disclosed herein may alsobe non-fillable, which means that they are not configured to be inflatedor filled with a separate substance such as a gas, liquid or solid inorder to provide a desired dimension of spacing between adjacent spinousprocesses, or in order to secure a fixation portion to a spinousprocess. Non-fillable implants may comprise continuous construction withno chambers, balloons or other enclosable areas capable of containing aseparate substance. The spacer members and other implant componentsdisclosed herein may also be flexible, which means they may flex whensubjected to sufficient force.

It is appreciated that implants disclosed herein may have spacers shapedto provide a consistent offset between the spinous processes, or thespacers may have a variable shape to provide a variable offset. Forexample, biomechanical studies could show that it is preferable to havea thicker offset either medially or laterally, in order to produce thedesired effects throughout a range of motion. The implants may alsoprovide initial progressive resistance to extension, followed by adefinite extension stop. This may be achieved by intrinsic springelements, compliant materials layered over rigid elements, orviscoelastic materials, among others. The actual proportions ofcompliant deflection combined with extension stop dimension are dictatedprimarily by patient anatomy and it is appreciated that a range of sizeswould be required up to and possibly beyond a 25 mm (1″) extension stop.The compliant deflection might be a percentage of the extension stopdimension, or a fixed increment.

All implants described herein may be implanted from a unilateralapproach, that is, the implantation procedure may be completed from onelateral side of the spine, or the other side. The choice of sides maydepend on surgeon preference or specific patient anatomicconsiderations. Implants which comprise the bracket 110 may beconfigured to be inserted, and attached to the spinous process fromeither lateral side. Additionally, implantation of the implants mayoccur without disturbing the supraspinous ligament.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. It isappreciated that various features of the above-described examples can bemixed and matched to form a variety of other alternatives. For example,the number of flanges can vary, as can the configuration of the spacermember. As such, the described embodiments are to be considered in allrespects only as illustrative and not restrictive. The scope of theinvention is, therefore, indicated by the appended claims rather than bythe foregoing description. All changes which come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

1. An implant comprising: a spacer sized to fit between first and secondadjacent spinous processes of a human spine to urge the maintenance of aminimum separation between the first and second spinous processes; and afixation portion coupled to the spacer, wherein the fixation portion isconfigured to permit insertion of the spacer between the first andsecond spinous processes from a lateral approach; wherein the fixationportion is securable to the first spinous process independently of thesecond spinous process to retain the spacer relative to the firstspinous process; wherein the spacer comprises an arcuate convex wall;wherein, when the spacer is between the first and second spinousprocesses and the fixation portion is secured to the first spinousprocess, the arcuate convex wall crosses a sagittal plane of the spine;wherein the spacer has a resilient configuration selected to providevariable resistive force urging the first and second spinous processesapart in response to extension of the spine.
 2. The implant of claim 1,wherein the spacer and the fixation portion are formed as a single piecewith each other.
 3. The implant of claim 1, wherein the fixation portioncomprises a bracket having an open configuration, in which the bracketis able to receive the first spinous process, and a closedconfiguration, in which the bracket at least partially encircles thefirst spinous process to securely grip the first spinous process therebyholding the spacer in a stable position relative to the first spinousprocess.
 4. The implant of claim 1, wherein the spacer is furtherconfigured to provide an extension stop that substantially preventsmotion of the second spinous process toward the first spinous processbeyond a threshold extension level.
 5. The implant of claim 1, furthercomprising: a tether configured to cooperate with the remainder of theimplant to fully encircle a selection of one of the first or secondspinous processes to retain the implant relative to the selected spinousprocess.
 6. An implant comprising: a spacer sized to fit between firstand second adjacent spinous processes of a human spine to urge themaintenance of a minimum separation between the first and second spinousprocesses; and a fixation portion coupled to the spacer, wherein thefixation portion is configured to be coupled to the first spinousprocess to retain the spacer relative to the first spinous process, thefixation portion comprising: a first flange coupled to a first end ofthe spacer and extending substantially orthogonal to a length of thespacer; and a second flange coupled to a second end of the spacer andextending substantially parallel to the first flange; wherein, when thespacer is between the first and second spinous processes, rotation ofthe spacer about a medial/lateral axis of the spine causes the first andsecond flanges to engage opposite lateral sides of the first spinousprocess to retain the implant relative to the first spinous process. 7.The implant of claim 6, wherein the spacer and the fixation portion areformed as a single piece with each other.
 8. The implant of claim 6,wherein the spacer is shaped to be inserted between the first and secondspinous processes from a lateral approach, wherein the fixation portionis further configured to be inserted along the lateral approach prior torotation of the spacer.
 9. The implant of claim 6, further comprising: atether configured to cooperate with the remainder of the implant tofully encircle a selection of one of the first or second spinousprocesses to retain the implant relative to the selected spinousprocess.
 10. The implant of claim 6, wherein the spacer comprises aninsertion feature shaped to connect to an instrument to receive torquetherefrom.
 11. An implant comprising: a spacer sized to fit betweenfirst and second adjacent spinous processes of a human spine to urge themaintenance of a minimum separation between the first and second spinousprocesses; and a fixation portion coupled to the spacer, wherein thefixation portion is configured to be coupled to the first spinousprocess to retain the spacer relative to the first spinous process;wherein, when the spacer is between the first and second spinousprocesses and the fixation portion is coupled to the first spinousprocess, a portion of the spacer is expandable along ananterior-posterior direction to restrict rotation of the spacer out of adesired orientation relative to the spine; wherein, after the spacerexpands, an anterior-posterior dimension of the spacer exceeds acephalad-caudal dimension of the spacer.
 12. The implant of claim 11,wherein the spacer and the fixation portion are formed as a single piecewith each other.
 13. The implant of claim 11, wherein the spacer isshaped to be inserted between the first and second spinous processesfrom a lateral approach.
 14. The implant of claim 11, furthercomprising: a tether configured to cooperate with the remainder of theimplant to fully encircle a selection of one of the first or secondspinous processes to retain the implant relative to the selected spinousprocess.
 15. The implant of claim 11, wherein the spacer comprises afirst portion and a second portion, wherein the first and secondportions are configured to move apart in the anterior and/or posteriordirection to define a gap between them.
 16. The implant of claim 15,wherein the first and second portions of the spacer are connected by aflexible flange of the fixation portion.